Two cycle engine



July 2, 1935. A. G. s. SHERMAN TWO CYCLE ENG INE Filed Feb. 29, 1932 2Sheets-Sheet 1 mr m Nu m W5 m .m

y 1935. A. G. s. SHERMAN 2,006,656

TWO-CYCLE ENGINE Filed Feb. 29, 1952 2 Sheets-Sheet 2 5 ATTORNEYPatented July 2, 1935 UNITED STATES PATENT OFFICE TWO CYCLE ENGINEArthur G. S. Sherman, Detroit, Mich.

Application February 29, 1932, Serial No. 595,856

6 Claims. (01. 123-65) This invention relates to internal combustionengines, and particularly to two-cycle en- 'gines.

WlL'le two-cycle engines have a decided advantage over four-cycleengines in simplicity of construction, cost of manufacture, the manitude of power output for a given size of engine, and low upkeepexpense, the four-cycle engine is largely preferred, in present daypractice, because of its superior reliability, more economical fuelconsumption, and adaptability to easy staring.

The disadvantages of the two-cycle engine primarily arise from use ofthe incoming fuel mixture to drive out spent gases by direct displacement. The resulting intermixture of the fuel charge and spent gaseshas heretofore unduly diluted such charge and permitted a considerableescape of unburned fuel during the concurrent periods of intake andexhaust.

Also it has been the general practice in twocycle engine design toeffect compression of the fuel mixture in the engine crank case, andthis has rendered starting laborious through necessity of initiallyfilling both the crank case and the cylinder with an explosive mixture.Crank case condensation of fuel, particularly prior to warming up of theengine, has also been a notable detriment.

An object of the invention is to make an improved provision for theadmission of a charge to a two-cycle engine, whereby segregation of theincoming charge from the spent gases will be largely increased overpresent practice, with correspondingly large reductions in the residueof spent gases contaminating the charge as compressed, and in the escapeof fuel with the spent gases.

Another object is to so admit the charge to a. two-cycle engine as tomaintain adjacent to the piston, throughout compression, a body ofuncontaminated fuel, which, on completion of the compression stroke,will lie in such proximity to the ignition means as to insure ignition.

Still another object is to arrange the intake and exhaust ports of atwo-cycle engine in an improved relation tending toward a more effectivescavenging, and toward a minimum exhaust of unburned fuel.

A further object is to introduce the fuel charge into an internalcombustion engine (and more particularly a two-cycle engine) .at avelocity and pressure independent of piston travel whereby difficulty isavoided in supplying the engine with a thoroughly combustible charge forstarting, and crank case compression, with its well-known disadvantages,is eliminated.

These and various other objects the invention attains by theconstruction hereinafter described and illustrated in the accompanyingdrawings, 9 5

Fig. 4 is a side elevational view of the engine.

In these views, the reference character I- designates the cylinder of atwo-cycle engine, 2 the crank case thereof, 3 the crank shaft, 4 thepiston, and 5 the connecting rod. In the wall of said cylinder is formedan intake port 6 to which fuel may be delivered from any suitable sourceby way of a duct 1, and said Wall is further formed with a pair ofexhaust ports 8 and 8, preferably adjacent to and at opposite sides ofthe port 6. limiting position, (Fig. 1) is adapted to uncover all threeports 6, 8 and 8.

The head of the piston 4 is diametrically formed with a fuel mixturepassage 9 having an inlet in the lateral face of the piston, registrablewith the port 6, when the piston is lowered. At its other end, saidpassage discharges into a pocket I9 opening both radially and upwardlyin the piston head, and having a'substantially vertical wall extendingin an approximately chordal relation to the piston, with preferably aslight curvature reentrant to the head. Preferably the top face of thepiston inclines upwardly at a gradual angle (as for example twentydegrees) toward the pocket [0, and it is also preferred to flare thepassage 9 transversely from its mid portion to its opening into saidpocket, as best appears in Fig. 3.

Suitable ignition means upon the top portion of the cylinder ispreferably positioned for registration with one or both extremities ofthe passage 9, when the engine is ready to fire. As illustrated, thisignition means comprises a pair of spark plugs I2 and I2 diametricallyopposed upon the cylinder; registering respectively with the pocket '10and the inlet of the passage 9, when the piston is raised. V To providefor uncovering of the exhaust ports 8 and 8 on completion of the powerThe piston 4 in its lower of any incoming mixture, nor does the latterof the piston stroke.

stroke, the piston is preferably formed with a pair of pockets l3, oneat each side of the inlet of the passage 9,,each opening jointly in thetop and lateral faces of the piston.

Delivery of fuel to the port 6 is accomplished independently of theengine crank case, and also Thus, preferably a blow er l4 driven by anelectric motor l5, delivers a stream of air at a suitablesuperatmospheric pressure to the port 6 by way of the duct 1 and in thelatter is interposed a carburetor 16, which. permits a predeterminedamount of fuel to be entrained by the air stream, in finely dividedvform. f Thus, in starting the engine, said motor and blower may beenergized independently of the piston travel, so as to promptly fill thecylinderwith a combustible mixture-and an adequate and proper mixturewill be assured throughout operation of the engine. v

Furthermore said mixture will be admitted at a considerably higherpressure and hence in considerably greater volume than is feasible wherecrank case compression is employed.

In operation of the described engine, the explosi've mixture deliveredto the passage 9 through the port '6, in the lowered position of thepiston, is. conducted by said passage across the piston head to thepocket l0. Encountering the cylinder wall in said pocket, the mixture isdeflected along said wall to the upper end of the cylinder, and is thereagain deflected ,by the cylinder head across the latter. In this manner,the cylinder is rapidly filled with the fuel mixture, which accumulatesfrom the cylinder'top downwardly, and also to a slight extent inwardlyfrom the side of the cylinder ad- 'jacent to the pocket l0. Since theinflowing mixture closely follows the cylinder wall, each increment ofthe charge of mixture displaces previously delivered increments awayfrom such wall and the cylinder top and toward the exhaust pockets l3,so that an initially delivered portion of the charge shields the balanceof the charge from contact with the spent gases during completescavenging of the latter. The spent gases are displaced throu h theexhaust ports 8 and 8, by the incoming mixture and contami-,

nation of the latter is almost completely avoided in delivering themixture as described, since the exhausting gases do not traverse thepath materially penetrate the body of spent gases. In thusavoidingcontamination of. the fuel mixture, delivery of the incoming mixtureacross the piston through a passage in the piston head is, a vitalfeature. Employment of said passage permits the exhausting gases andincoming mixture to concurrently flow through closely adjacent ports,while positively and completely, isolating said gases and mixturefromeach other in the vicinity of said ports, and maintains this isolationuntil the mixture has reached a point diametrically opposed to saidports.

Also said passage assures maintenance, during 'the; compression stroke,of a portion of thejmixture completely free of contamination in such a'definite proximity to the piston head that prompt and certain ignitionwill take place on registration of said piston withthe spark plugs, atthe instant of firing. i 1

"Operation of two-cycle engines, as heretofore constructed, is oftenrendered defective by, four cycling, or firing only on alternatecompressions. This is due to such impoverishment of 75 the 'compres'sedcharge by spentgases as to reclosed maintains uniformity of fuelthroughout v the intake period.

The high pressure introduction of fuel is a factor of importance inpreventing appreciable mixing of the fuel and exhaust gases since thepressure imposes a velocity upon the incoming fuel such as carries itforcefully along the desired path. without diffusion.

By flowing the fuel mixture through the piston head, as described, thefuel temperature is materially raised prior to ignition, thusfacilitating combustion, and the piston is sufficiently cooled tosafeguard it from heat damage.

While it is apparent that the illustrated embodiment of my invention iswell calculated to adequately fulfill the objects and advantagesprimarily stated, it is to be understood that the invention issusceptible to variation, modification and change within the spirit andscope of the subjoined claims.

What I claim is: t

1. In a two-cycle engine, the combination with a cylinder formed with anintake and exhaust port, of a piston reciprocatory in said cylinder andhaving an approximately diametrical intake passage opening at one end inthe end face of the piston in close proximity to the cylinder wall, theother end of said passage being registrable on approximate completionof. the power stroke with said intake port, said piston being furthermarginally formed with an exhaust pocket opening upwardly, and alsoopening toward the cylinder wall, registrable with said exhaust port oncompletion of thepower stroke.

2. A two-cycle engine, comprising a cylinder having intake and exhaustports, a piston reciprocatory in said cylinder having a fuel passage andhaving a pocket opening in the. end face of the piston at the margin ofsaid face, said passage having an inlet, opening laterally in the pistonand having an outlet opening into said pocket, registrable'with saidintake port upon completion of the. power stroke, said exhaust portbeing uncovered by the piston upon completion of the power stroke, anddual ignition means upon the cylinder registrable with said pocket andwith the inlet of said passage upon completion of the compressionstroke.

3. A two-cycle engine comprising a cylinder having an intake port andexhaust port, and a piston reciprocatory in said cylinder, and havingits head marginally formed with an intake pocket and an exhaust pocket;each opening upwardly and also opening toward the cylinder wall, saidexhaust pocket being registrable with said exhaust port, uponapproximate completion of the power stroke, the piston being furtherformed with an intake passage, registrable at one end with the intakeport upon approximate completion. of the power stroke, said passageopening at its other end into the intake pocket, toward the cylinderwall.

4. A. two cycle engine comprising a cylinder, a piston reciprocating insaid cylinder, having a fuel passage and an outlet to the cylinder fromone end of said passage, means for delivering fuel to the other end ofsaid passage in a substantially limiting position of reciprocation ofsaid piston, and dual ignition means upon the cylinder registrable withboth ends of said passage substantially in the other limiting positionof piston reciprocation.

5. In a two cycle engine, the combination with a cylinder having anintake port, of a piston reciprocatory in said cylinder and formed, in asubstantially diametrical relation to the piston, with an intake passageregistrable at one of its. ends with said intake port, on approximatecompletion of the power stroke, said piston being further formed with apocket connected to the other end of said passage, opening toward thecylinder wall and also opening upwardly, said pocket being closed by thecylinder wall at the sides of said passage, whereby the discharge offluid from said passage is restricted to an upward direction along thecylinder wall.

6. In a two cycle engine, the combination with a cylinder having anintake port, of a piston reciprocatory in said cylinder and formed, in asubstantially diametrical relation to the piston, with an intake passageregistrable at one of its ends with said intake port, on approximatecompletion of the power stroke, said passage opening at its other end ina wall of the piston which wall extends between circumferentially spacedpoints of the cylinder wall, and forms with the cylinder wall a pocketopening only in an upward direction, whereby fuel discharging from saidpocket is limited to an upward direction and restrained in its tendencyto diffuse.

ARTHUR G. S. SHERMAN.

